1. Field of the Invention
The present invention relates to a liquid ejection head and a manufacturing method thereof.
2. Description of the Related Art
As an example of a liquid ejection head for ejecting liquid, there is known an ink jet recording head used for an ink jet printing method in which small ink droplets are ejected and applied to a recording medium such as paper.
With the advancement of the recording technologies in recent years, for the ink jet recording head, it is required that the density of array of ejection orifices for ejecting ink should be made higher, and the shapes of the ejection orifices and flow paths communicating thereto should be fabricated more minutely. Japanese Patent Application Laid-Open No. H06-286149 discloses a method of manufacturing a liquid ejection head in which a nozzle layer is formed on a silicon wafer, which has been provided in advance with heater elements and driving circuits, with a resin which can be patterned by photolithography.
However, as the diameter of the ink ejection orifice becomes smaller for addressing a further degree of micro-fabrication, the ink ejection orifice, which is fabricated more minutely, may be clogged with dust in ink, thereby hindering normal ejection.
For addressing this problem, Japanese Patent Application Laid-Open No. 2005-178364 discloses, for collecting dust in ink, a nozzle structure provided with a filter part having an opening diameter smaller than an opening diameter of an ink ejection orifice. More concretely, there is disclosed a nozzle structure for collecting dust in ink by providing a free standing monolayer film (so called membrane) between a substrate on which driving circuits are formed and a nozzle layer, and forming through holes in the film.
However, the conventional filter structure collects dust in ink on the surface of the filter, and hence dust is apt to reach the through holes of the filter. Therefore, after collecting dust, as illustrated in FIG. 5, the through holes of the filter may be clogged with dust 10. This decreases the ink flow rate to decrease the supply rate of the ink required for ejection. As a result, blurs and unevenness of printed images may be caused.